I use a Anker bluetooth keyboard and it's really good. It's not mechcanical, but it does work on Mac, Windows, iOS, and Android. It's $20 at my nearest Walmart.
I want to build a PC for a friend, and I wonder how much RAM should I put in, I think he said he will use it for video and picture editing, streaming, and some gaming.
I also think that future-proofing is kind of dumb. In no possible way can you build a great PC now in 2017 and expect it to crush games in about 10 or 15 years. Even Threadripper will be obsolete in a long time.
I'm not judging your build (btw it is a good build in my opinion) but I think the GTX 1080 is getting a little old. It's still a good and expensive card, but I recommend the 1080 TI if you can.